Technical Field
The present invention relates to a steel alloy, more specifically for application on railway components, which chemical composition promotes the enhancement of many of its mechanical properties, more particularly fatigue strength.
Description of Related Art
In the last few years, rail shipping has considerably increased due to a growing demand for high capacity transport. This demand has created a need to increase the volume of goods being carried in a train, which has led to an increase in the number of railway freight cars. Moreover, railway freight cars have been designed to have bigger capacity.
As the volume of goods being carried in a train has increased, so has the need for mechanical railway components. The most required components include shock and traction systems, responsible for the safe coupling of the locomotive with the carriages.
Besides safe operation, flexibility, standardization and easy operation are vital features of the said systems. They must ensure the quick coupling and uncoupling of the cars as well as transfer the traction and compression effort along the train, within established limits.
After simulations are run and data on the instrumented cars analyzed, it was noticed that the shock and traction systems of the current railway cars are being subjected to extreme longitudinal effort, which substantially increases the risk of failure and increases preventive and corrective maintenance costs.
Naturally, one of the problems arising from the increase in the volume of goods being carried in a train is that the alloy utilized to produce the components of the shock and traction system of each car is no longer suitable for that.
More specifically, the composition of the steel alloys that are commonly utilized to manufacture railway car components do not favor the condition of extreme longitudinal effort the shock and traction system undergoes. An example is the alloy disclosed by U.S. Pat. No. 2,447,089, which has high tensile and impact strength and is suitable for railway and automotive industries.
The chemical composition of the alloy disclosed by U.S. Pat. No. 2,447,089 is 0.15-0.4% carbon, 1.0-2.5% manganese, 0.8-3.0% silicon, 1.0-5.0% nickel and 0.25-1.0% molybdenum. Although the abovementioned ranges are useful for imparting various beneficial mechanical characteristics to components of the railway composition, the chemical composition causes several problems that render it currently inappropriate for use, like the absence of titanium, which works as a grain size refiner and reduces the harmful effects of nitrogen, and the lack of the specification of maximum phosphorus and sulfur levels, which are vital elements to all the mechanical properties desirable in a shock and traction system. Furthermore, manganese is in a range “too high” for hardened and tempered steel and may compromise the said alloy's toughness.
Another alloy known in the art and that exhibits mechanical capacity issues is the one disclosed by U.S. Pat. No. 5,482,675. Such alloy—as reported by the said document—is specific for railway cars and has the following chemical composition: from 0.15 to 0.21% carbon, from 0.9 to 1.3% manganese, from 0.35 to 0.65% silicon, from 0.25 to 0.6% chromium, from 0.1 to 0.3% molybdenum, up to 0.025% phosphorus and up to 0.025% sulfur. However, once again titanium was not utilized, and the maximum phosphorus and sulfur levels are way too high for the current standard, thereby compromising certain desirable features, like toughness, for example. Nickel, which improves toughness and synergistically works with chromium and molybdenum, is lacking too.
Therefore, a steel alloy suitable for railway car components—more specifically for components of the railway car shock and traction system—, which promotes enough mechanical properties to endure the effort the cars are subjected to with the current cargo demand, is not known in the art.